Patent Application
20250058422
The present invention relates to a method of grinding a wafer.
Chips including devices such as integrated circuits (ICs), for example, are components that are indispensable for various types of electronic equipment including cellular phones and personal computers. Such chips are manufactured by dividing wafers with a plurality of devices formed on their face side into pieces each containing one of the devices.
Occasionally, for reducing the size of chips to be fabricated from a wafer, it is customary to thin down the wafer, which has a plurality of devices formed on a face side thereof, before it is divided into chips. For example, a grinding apparatus is used to thin down the wafer by grinding a reverse side thereof that is opposite the face side. In general, the grinding apparatus includes a chuck table that has a substantially horizontal holding surface for holding a wafer thereon and that is rotatable about a vertical axis extending straight through a center of the holding surface and a spindle disposed above the chuck table and extending vertically. The spindle is vertically movable and rotatable about its vertical longitudinal axis.
A grinding wheel with an annular array of circumferentially spaced grindstones on a lower surface thereof is mounted on the lower end, i.e., distal end, of the spindle. The grinding wheel is designed such that the outside diameter of a circular track followed by the lower grinding surface of each of the grindstones at a time at which the spindle and hence the grinding wheel are rotated is longer than the radius of a wafer held on the chuck table.
The grinding apparatus thins down a wafer as follows: First, the wafer is held on the holding surface of the chuck table with the reverse side of the wafer being exposed upwardly. Then, the chuck table and the spindle are adjusted in their relative positions such that the center of the wafer is positioned immediately below the track of the lower grinding surface of each of the grindstones as they are circularly moved upon rotation of the spindle.
Thereafter, both the chuck table and the spindle are rotated and the spindle is lowered to bring the grindstones into abrasive contact with the reverse side of the wafer, starting to grind the wafer. While the chuck table and the spindle are being rotated, the spindle is continuously lowered to grind the wafer until the wafer reaches a desired thickness. The reverse side of the wafer is ground in its entirety, and the wafer is thinned down.
When the entire reverse side of the wafer is thinned down, the wafer may be reduced in rigidity possibly to the extent that it might be difficult to handle in subsequent steps. One solution has been to grind the reverse side of a wafer according to a grinding process called “TAIKO grinding process” (see, for example, Japanese Patent Laid-Open No. 2007-19461).
According to the TAIKO grinding process, in short, the reverse side of a wafer is ground by an annular array of grindstones on a grinding wheel mounted on the lower distal end of a spindle when the spindle is rotated about its vertical central axis. At this time, the outside diameter of a circular track followed by the lower grinding surface of each of the grindstones is shorter than the radius of the wafer. Therefore, the grindstones grind the reverse side, i.e., the upper surface, of a central region of the wafer, leaving a region surrounding the central region, i.e., an outer excessive circumferential region, of the wafer unground as a ring-shaped stiffener portion.
When the reverse side of the wafer is ground in this manner, a recess having a circular bottom is formed in the reverse side of the wafer by the grindstones. During the grinding process from the time when the wafer starts being ground until the recess having a predetermined shape is formed in the reverse side of the wafer, the grindstones have respective outer side surfaces kept in contact with a circular side surface of the wafer that defines the recess, i.e., an inner circular side surface of the ring-shaped stiffener portion. Consequently, the ring-shaped stiffener portion tends to be broken or chipped near the inner circular side surface thereof due to contact with the grindstones.
In view of the above difficulty, it has been proposed to carry out the TAIKO grinding process such that the outer side surfaces of the respective grindstones contact the inner circular side surface of the ring-shaped stiffener portion in a reduced period of time (see, for example, Japanese Patent Laid-Open No. 2021-150347). Specifically, the spindle is slightly tilted sideways from the vertical directions in order for the track followed by the lower grinding surface of each of the grindstones at a time at which the spindle is rotated about its vertical central axis to have a portion that is positioned immediately above the center of the wafer and that is the lowest of the remainder of the track.
Then, with the spindle being thus tilted, the TAIKO grinding process is carried out on the wafer in a first grinding step. In the first grinding step, the grindstones form a first recess whose bottom is of a shape represented by the side surface of an inverted cone in the reverse side of the wafer as a result of the spindle being tilted, while the outer side surfaces of the grindstones being kept out of contact with the inner circular side surface of the ring-shaped stiffener portion of the wafer.
Then, the first grinding step is continuously followed by a second grinding step in which the spindle is tilted back to its original orientation along the vertical directions and the TAIKO grinding process is carried out on the wafer. In the second grinding step, the grindstones form a second recess whose bottom lies as a flat circular surface in the reverse side of the wafer.
As a result of the proposed version of the TAIKO grinding process, it is possible to fabricate a wafer whose central region has been thinned down to a uniform thickness without causing the wafer to be chipped near the inner circular side surface of the ring-shaped stiffener portion due to contact with the grindstones.
However, when the second grinding step is carried out in a manner to continuously follow the first grinding step, the grindstones are liable to impose a large load on an outer corner of the first recess, i.e., near the outer edge of the bottom of the first recess. Under the large load thus imposed, the wafer is likely to crack in the corner of the first recess and hence to be damaged.
In view of the above shortcomings, it is an object of the present invention to provide a method of grinding a wafer while reducing the probability of a processing fault such as chippings or cracks on the wafer when a recess having a circular bottom is formed on the reverse side of the wafer.
In accordance with an aspect of the present invention, there is provided a method of grinding a wafer on a grinding apparatus including a chuck table that has a holding surface and that is rotatable about a first rotational axis passing through a center of the holding surface, a spindle rotatable about a second rotational axis, and a grinding wheel mounted on a distal end of the spindle and supporting thereon an annular array of grindstones disposed at spaced intervals, the wafer having a face side with a plurality of devices formed thereon and a radius longer than an outside diameter of a track to be followed by a grinding surface of each of the grindstones when the spindle is rotated, the method including a holding step of holding the wafer on the holding surface of the chuck table with a reverse side of the wafer that is opposite the face side thereof being exposed, after the holding step, a first grinding step of grinding the reverse side of the wafer by keeping a center of the wafer and the track superposed on each other in a predetermined direction while rotating the chuck table and the spindle respectively about the first rotational axis and the second rotational axis, and moving the chuck table and the spindle closer to each other in the predetermined direction to bring the grindstones into abrasive contact with the reverse side of the wafer, after the first grinding step, a separating step of spacing the chuck table and the spindle from each other in a direction opposite the predetermined direction to separate the grindstones and the reverse side of the wafer from each other, after the separating step, an adjusting step of adjusting a tilt of at least one of the chuck table or the spindle to change an angle formed between the first rotational axis and the second rotational axis, and after the adjusting step, a second grinding step of grinding the reverse side of the wafer by keeping the center of the wafer and the track superposed on each other in the predetermined direction while rotating the chuck table and the spindle respectively about the first rotational axis and the second rotational axis, and moving the chuck table and the spindle closer to each other in the predetermined direction to bring the grindstones into abrasive contact with the reverse side of the wafer. The first grinding step includes forming a first recess whose bottom is of a shape represented by a side surface of an inverted cone in the reverse side of the wafer, and the second grinding step includes forming a second recess whose bottom is of a circular shape in the reverse side of the wafer.
Preferably, the method of grinding a wafer should further include, after the separating step and before the second grinding step, a cleaning step of cleaning the bottom of the first recess. Moreover, the method of grinding a wafer should further include, after the separating step and before the second grinding step, a position adjusting step of moving the chuck table and the spindle toward or away from each other in a direction perpendicular to the predetermined direction.
According to the present invention, after the first grinding step and before the second grinding step, the chuck table and the spindle are spaced from each other in order to separate the grindstones and the reverse side of the wafer from each other, and then the tilt of at least one of the chuck table or the spindle is adjusted to change the angle formed between a rotational axis about which the chuck table is rotatable, i.e., the first rotational axis, and a rotational axis about which the spindle is rotatable, i.e., the second rotational axis.
According to the present invention, therefore, the tilt of at least one of the chuck table or the spindle is not adjusted while the grindstones and the reverse side of the wafer are being kept in contact with each other. Consequently, the angle formed between the rotational axis of the chuck table and the rotational axis of the spindle is changed without imposing a load on areas near the outer edge of the bottom of the first recess. As a result, according to the present invention, it is possible to reduce the probability of a processing fault such as chippings or cracks on the wafer when the second recess having the circular bottom is formed in the reverse side of the wafer.
The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing an embodiment of the invention.
A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.
The grinding apparatus, denoted by 2 in
A screw shaft 12 that extends along the X-axis is disposed between the guide rails 8. The screw shaft 12 has an end coupled to a stepping motor 14 for rotating the screw shaft 12 about its central axis. A nut 16 that houses therein a number of balls, not depicted, that can circulate through helical grooves, not depicted, upon rotation of the screw shaft 12 is threaded over an externally threaded outer surface of the screw shaft 12. The nut 16, the balls, and the screw shaft 12 jointly make up a ball screw mechanism.
The nut 16 is fixed to a lower surface of the X-axis movable plate 10. When the stepping motor 14 is energized, it rotates the screw shaft 12 about its central axis, moving the nut 16 and the X-axis movable plate 10 along the X-axis. A chuck table 18 shaped as a circular plate that is movable along the X-axis in unison with the X-axis movable plate 10 is disposed above the X-axis movable plate 10.
The chuck table 18 has a frame 20 shaped as a circulate plate and made of ceramic. The frame 20 has a circular recess defined in an upper surface thereof and having a predetermined depth. The frame 20 includes a fluid channel, not depicted, that is defined therein and that has an upper end open at the bottom of the recess. The fluid channel is fluidly connected to a suction source, not depicted, such as an ejector.
The chuck table 18 also includes a circular porous plate 22 that has essentially the same diameter as the recess and that is fitted in the recess. The porous plate 22 is made of porous ceramic, for example. The porous plate 22 has an upper surface shaped like the side surface of a cone, i.e., having a center protruding upwardly beyond an outer circumferential edge thereof.
When the suction source fluidly connected to the fluid channel in the frame 20 is actuated, the suction source generates and transmits a suction force through the fluid channel to a space in the vicinity of the upper surface of the porous plate 22. Therefore, the upper surface of the porous plate 22 and an upper surface of the frame 20 that lies flush with the upper surface of the porous plate 22 function as a holding surface of the chuck table 18 for holding the wafer thereon.
A rotating mechanism, not depicted, for rotating the chuck table 18 about its vertical central axis is disposed below the chuck table 18. The rotating mechanism includes a pulley and a servomotor, both not depicted, for example. When the rotating mechanism is actuated, the chuck table 18 is rotated about its vertical central axis, i.e., a first rotational axis, that extends straight through the center of the holding surface.
The chuck table 18 is rotatably supported on a hollow cylindrical bearing 24 and a hollow cylindrical support plate 26 that are disposed beneath the chuck table 18. The chuck table 18 is rotatably coupled to a chuck table adjusting mechanism 28 through the bearing 24 and the support plate 26.
The chuck table adjusting mechanism 28 has two axially movable shafts 28a and 28b and a single fixed shaft 28c that are spaced at substantially equal angular intervals circumferentially around the chuck table 18 and that have respective lower ends fixed to an upper surface of the X-axis movable plate 10. When at least one of the axially movable shaft 28a or the axially movable shaft 28b is axially moved to lift or lower a corresponding portion of the chuck table 18, the tilt of the vertical central axis of the chuck table 18 is adjusted.
The chuck table adjusting mechanism 28 is coupled to the chuck table 18 such that a line segment interconnecting a point positioned on an outer circumferential edge of the holding surface of the chuck table 18 along the X-axis as viewed from the center of the holding surface and the center of the holding surface extends parallel to the X-axis in an initial state of the grinding apparatus 2.
An upstanding wall 30 that extends vertically along the Z-axis is mounted on an end of the foundation base 4. The wall 30 supports a Z-axis moving mechanism 32 on a surface thereof that faces the chuck table 18. The Z-axis moving mechanism 32 includes a pair of guide rails 34 each extending along the Z-axis. A Z-axis movable plate 36 shaped as a rectangular parallelepiped is slidably mounted on the guide rails 34 for sliding movement therealong, i.e., along the Z-axis.
A screw shaft 38 that extends along the Z-axis is disposed between the guide rails 34. The screw shaft 38 has one end (an upper end) coupled to a stepping motor 40 for rotating the screw shaft 38 about its central axis. A nut 42 that houses therein a number of balls, not depicted, that can circulate through helical grooves, not depicted, upon rotation of the screw shaft 38 is threaded over an externally threaded outer surface of the screw shaft 38. The nut 42, the balls, and the screw shaft 38 jointly make up a ball screw mechanism.
The nut 42 is fixed to a rear surface of the Z-axis movable plate 36 that faces the wall 30. When the stepping motor 40 is energized, it rotates the screw shaft 38 about its central axis, moving the nut 42 and the Z-axis movable plate 36 along the Z-axis. A bottomed hollow cylindrical cover 44 is secured to a front surface of the Z-axis movable plate 36 that faces away from the wall 30. The cover 44 has a through hole 44a defined centrally in its bottom through which a spindle 52 to be described below extends substantially vertically.
The cover 44 accommodates a housing 46 therein. The housing 46 is supported on the bottom of the cover 44 by two spacers 48a and 48b. The spacer 48a is spaced from the spindle 52 in one direction along the X-axis, whereas the spacer 48b is spaced from the spindle 52 in the opposite direction along the X-axis.
The housing 46 is coupled to a spindle adjusting mechanism 50. The spindle adjusting mechanism 50 has a bolt 50a including a shank threaded through an internally threaded hole vertically defined in a portion of the bottom of the cover 44 that is positioned beneath the spacer 48a and extending into an internally threaded hole that is defined in the spacer 48a and open downwardly, and a head joined to a lower end of the shank and positioned beneath the bottom of the cover 44.
The bolt 50a is coupled to a stepping motor, not depicted, for rotating the bolt 50a about its vertical central axis. When the stepping motor is energized, it rotates the bolt 50 clockwise, for example, as viewed from below, lifting the spacer 48a. Specifically, the spacer 48a can be lifted off the bottom of the cover 44 until the head of the bolt 50a is brought into contact with the bottom of the cover 44.
When the stepping motor is reversed, it rotates the bolt 50 counterclockwise, for example, as viewed from below, lowering the spacer 48a. Specifically, the spacer 48a can be lowered to separate the head of the bolt 50a from the bottom of the cover 44 until the spacer 48a is brought into contact with the bottom of the cover 44. The spindle adjusting mechanism 50 is coupled to the housing 46 such that the spacer 48a is kept in contact with the bottom of the cover 44 and the head of the bolt 50a is separate from the bottom of the cover 44 in the initial state of the grinding apparatus 2.
In the initial state, the spindle 52 that extends substantially vertically along the Z-axis is partly housed rotatably in the housing 46. The housing 46 also houses a servomotor, not depicted, coupled to an upper proximal end of the spindle 52 for rotating the spindle 52 about its central axis. The remainder of the spindle 52 extends downwardly from the housing 46 and protrudes out of the cover 44 through the through hole 44a that is defined centrally in the bottom of the cover 44. The spindle 52 has a lower distal end disposed below the bottom of the cover 44 and supporting thereon a wheel mount 54 shaped as a circular plate.
The wheel mount 54 is made of a metal material such as stainless steel, for example, and has a generally flat lower surface. The wheel mount 54 also has a plurality of through holes, not depicted, defined in an outer circumferential portion thereof and spaced at substantially equal angular intervals circumferentially around the wheel mount 54. A grinding wheel 56 is mounted on the lower surface of the wheel mount 54 by a plurality of fasteners, not depicted, such as bolts inserted respectively through the through holes in the wheel mount 54.
The grinding wheel 56 includes an annular wheel base 58 made of a metal material such as stainless steel, for example. The wheel base 58 has a lower surface on which an annular array of angularly spaced grindstones 60 is mounted. Each of the grindstones 60 is made of a binder such as a vitrified bond or a resinoid bond and abrasive grains of diamond dispersed in the binder. The grindstones 60 have respective lower surfaces where abrasive grains are exposed. The lower surfaces of the respective grindstones 60 function as grinding surfaces for grinding wafers.
When the servomotor coupled to the proximal end of the spindle 52 is energized, it rotates the spindle 52 and hence the grindstones 60 about their central axis, i.e., a second rotational axis, that extends straight along the spindle 52. When the spindle 52 is rotated, the grinding surface of each of the grindstones 60 follows an annular track whose outside diameter is slightly shorter than the diameter of the porous plate 22 of the chuck table 18, for example.
When the spindle adjusting mechanism 50 is actuated to lift the spacer 48a off the bottom of the cover 44, the tilt of the spindle 52, the wheel mount 54, and the grinding wheel 56 is adjusted to position those of the grindstones 60 that are farther from the wall 30 lower than those of the grindstones 60 that are closer to the wall 30. In other words, the spindle adjusting mechanism 50 is actuated in order to adjust the tilt of the second rotational axis about which the spindle 52 rotates. In the initial state where the spacer 48a is in contact with the bottom of the cover 44, the second rotational axis about which the spindle 52 rotates extends parallel to the Z-axis.
The through holes 64a defined in the boss 64 are held in fluid communication with a liquid supply source, not depicted, such as a pump for supplying liquid such as water, via the fluid channel 62a defined in the base 62 and the fluid channel 52a defined in the spindle 52. When the liquid supply source is actuated, it supplies liquid through the fluid channel 52a, the fluid channel 62a, and the through holes 64a radially outwardly into a space defined in an inner lower portion of the grinding wheel 56.
The wafer 11 has a face side 11a including a plurality of areas demarcated by a grid of projected dicing lines or streets 13, with a plurality of devices 15 such as ICs being formed in the respective areas. The devices 15 are arrayed in rows and columns within a circular central region 17a of the wafer 11 and do not exist in an annular outer circumferential excessive region 17b surrounding the central region 17a.
The radius of the central region 17a of the wafer 11 is substantially equal to the outside diameter of the track followed by the grinding surfaces of the grindstones 60 at the time when the spindle 52 is rotated. In
A protective tape 19 shaped as a circular sheet is affixed to the face side 11a of the wafer 11 for protecting the devices 15 from being broken during the grinding of the reverse side 11b. The protective tape 19, which is essentially equal to the wafer 11 in diameter, includes a flexible film-shaped base layer and an adhesive layer, i.e., a glue layer, provided on a surface of the base layer that faces the wafer 11.
Specifically, the base layer is made of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), or polystyrene (PS), for example. The adhesive layer is made of ultraviolet-curable silicone rubber, an acryl-based material, or an epoxy-based material, for example.
In the holding step S1, the wafer 11 is placed on the holding surface of the chuck table 18 with the protective tape 19 interposed therebetween such that the center of the holding surface of the chuck table 18 is aligned with a center of a surface of the protective tape 19 that faces the chuck table 18. Then, the suction source that is fluidly connected to the fluid channel defined in the frame 20 of the chuck table 18 is actuated to apply a suction force, i.e., a negative pressure, holding the wafer 11 under suction on the holding surface of the chuck table 18 with the reverse side 11b of the wafer 11 being exposed upwardly.
After the holding step S1, the tilt of the spindle 52 is adjusted in order to form a first recess whose bottom is of a shape represented by the side surface of an inverted cone in the reverse side 11b of the wafer 11 in first grinding step S3 to be described later (first adjusting step S2).
In the first adjusting step S2, specifically, the spindle adjusting mechanism 50 is actuated to lift the spacer 48a to put the angle θ between the rotational axis A, i.e., the second rotational axis, of the spindle 52 and a straight line L parallel to the Z-axis in a range larger than 0° but smaller than 2°, for example. Therefore, the grinding surfaces of the grindstones 60 that are farther from the wall 30 are positioned lower than those of the grindstones 60 that are closer to the wall 30.
After the first adjusting step S2, the reverse side 11b of the wafer 11 is ground to form a first recess therein (the first grinding step S3).
In the first grinding step S3, the chuck table 18 is moved along the X-axis to position the center of the holding surface of the chuck table 18 immediately below a lowermost portion of the track of the lower grinding surface of each of the grindstones 60 as they are circularly moved upon rotation of the spindle 52.
Then, while both the chuck table 18 and the spindle 52 are being rotated and the liquid, not depicted, from the liquid supply source is being supplied via the fluid channel 52a, the fluid channel 62a, and the through holes 64a into the space defined in the inner lower portion of the grinding wheel 56, the spindle 52 is lowered to bring the grindstones 60 into abrasive contact with the reverse side 11b of the wafer 11 on the chuck table 18. The wafer 11 now starts being ground by the grindstones 60.
While both the chuck table 18 and the spindle 52 are being rotated and the liquid is being supplied from the grinding wheel 56 to the reverse side 11b of the wafer 11, the spindle 52 is continuously lowered to grind the wafer 11 until the thickness of the center of the wafer 11 reaches a predetermined thickness. The predetermined thickness is either equal to or slightly larger than the thickness of the central region 17a of the wafer 11 available after second grinding step S6 to be described later.
In the first grinding step S3, the grindstones 60 grind the reverse side 11b of the wafer 11 until they form a first recess 21 having a bottom 21a that is of a shape represented by the side surface of an inverted cone in the reverse side 11b. When the reverse side 11b of the wafer 11 is ground, debris or swarf is produced from the wafer 11 and the grindstones 60 and exist on the reverse side 11b. Most of the swarf is washed away by the liquid supplied to the reverse side 11b.
In the first grinding step S3, since the rotational axis A of the spindle 52 is tilted by the angle θ from the straight line L parallel to the Z-axis, the outer side of each of the grindstones 60 is held out of contact with a side surface 21b of the first recess 21. Consequently, the wafer 11 is prevented from being chipped by the grindstones 60 that would otherwise contact the side surface 21b in the second grinding step S6.
Thereafter, the spindle 52 is lifted to separate the grindstones 60 upwardly from the reverse side 11b of the wafer 11 (separating step S4).
In the separating step S4, the spindle 52 is lifted until the grindstones 60 are positioned above at least the annular outer circumferential excessive region 17b of the wafer 11. After the spindle 52 has been lifted in this manner, both the chuck table 18 and the spindle 52 may or may not stop being rotated.
After the separating step S4, the tilt of the spindle 52 is adjusted in order to form a second recess whose bottom is of a circular shape in the reverse side 11b of the wafer 11 in the second grinding step S6 to be described later (second adjusting step S5).
In the second adjusting step S5, the spindle 52 is tilted back to its original state to change the angle formed between the rotational axis, i.e., the first rotational axis, of the chuck table 18 and the rotational axis, i.e., the second rotational axis, of the spindle 52. Specifically, the spindle adjusting mechanism 50 is actuated to lower the spacer 48a into contact with the bottom of the cover 44 in order to make the rotational axis of the spindle 52 parallel to the Z-axis.
After the second adjusting step S5, the reverse side 11b of the wafer 11 is ground to form a second recess therein (the second grinding step S6).
In the second grinding step S6, the components of the grinding apparatus 2 are operated to start grinding the wafer 11 in the same manner as with the first grinding step S3. While both the chuck table 18 and the spindle 52 are being rotated, the spindle 52 is lowered to bring the grindstones 60 into abrasive contact with the reverse side 11b of the wafer 11, and the reverse side 11b is ground until the thickness of the central region 17a of the wafer 11 reaches a predetermined thickness. The grindstones 60 as they grind the reverse side 11b form a second recess 23 having a bottom 23a that is of a circular shape in the reverse side 11b.
According to the method of grinding a wafer as illustrated in
According to the method, therefore, the tilt of at least one of the chuck table 18 or the spindle 52 is not adjusted while the grindstones 60 and the reverse side 11b of the wafer 11 are being kept in contact with each other. Consequently, the angle formed between the rotational axis of the chuck table 18 and the rotational axis of the spindle 52 is changed without imposing a load on areas near the outer edge of the bottom 21a of the first recess 21. As a result, it is possible to reduce the probability of a processing fault such as chippings or cracks on the wafer 11 when the second recess 23 having the circular bottom 23a is formed in the reverse side 11b of the wafer 11.
The details described above belong to the embodiment of the present invention, but the present invention is not limited to the above details. According to the present invention, the rotational axis of the spindle 52 may be inclined to the Z-axis in advance. In other words, the spacer 48a may be coupled to the housing 46 while being separate from the bottom of the cover 44 in the initial state. In this case, the first adjusting step S2 may be omitted.
Moreover, according to the present invention, in at least one of the first adjusting step S2 or the second adjusting step S5, only the tilt of the chuck table 18 may be adjusted without the tilt of the spindle 52 being adjusted. Alternatively, according to the present invention, in at least one of the first adjusting step S2 or the second adjusting step S5, the tilt of both the chuck table 18 and the spindle 52 may be adjusted.
Furthermore, the present invention may cover a method of grinding a water that includes other steps than the steps S1 through S6 illustrated in
If the position along the X-axis of the track followed by the lower grinding surface of each of the grindstones 60 at a time at which the spindle 52 is rotated tends to be different before and after the second adjusting step S5, then a position adjusting step of moving the chuck table 18 along the X-axis may be carried out after the separating step S4 and before the second grinding step S6.
For example, if the track followed by the lower grinding surface of each of the grindstones 60 is positioned in its entirety within the first recess 21 as viewed in plan after the second adjusting step S5, then the chuck table 18 and the spindle 52 may be spaced from each other along the X-axis in order to have a point positioned on the side surface 21b of the first recess 21 along the X-axis as viewed from the center of the wafer 11 superposed on an end of the track along the X-axis.
On the other hand, if a portion of the track followed by the lower grinding surface of each of the grindstones 60 is positioned outside of the first recess 21 as viewed in plan after the second adjusting step S5, then the chuck table 18 and the spindle 52 may be moved closer to each other along the X-axis in order to have a point positioned on the side surface 21b of the first recess 21 along the X-axis as viewed from the center of the wafer 11 superposed on an end of the track along the X-axis.
Moreover, for intentionally making the diameter of the second recess 23 formed in the reverse side 11b of the wafer 11 in the second grinding step S6 and the diameter of the first recess 21 different from each other, the position adjusting step of moving the chuck table 18 along the X-axis may be carried out after the separating step S4 and before the second grinding step S6.
For example, for forming the second recess 23 that is shorter in diameter than the first recess 21, the chuck table 18 and the spindle 52 may be moved closer to each other along the X-axis in order to position the entire track radially inwardly of the side surface 21b of the first recess 21 as viewed in plan.
On the other hand, for forming the second recess 23 that is longer in diameter than the first recess 21, the chuck table 18 and the spindle 52 may be moved farther from each other along the X-axis in order to position a portion of the track radially outwardly of the side surface 21b of the first recess 21 as viewed in plan.
The structural and methodical details described above according to the present embodiment may appropriately be changed or modified without departing from the scope of the invention.
The present invention is not limited to the details of the above described preferred embodiment. The scope of the invention is defined by the appended claims and all changes and modifications as fall within the equivalence of the scope of the claims are therefore to be embraced by the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-131778 | Aug 2023 | JP | national |
